Technical Field
The present invention relates to a directional drilling system comprising a four-motor drilling head driving four independent bit assemblies positioned in a front face plane of the drilling head, independently controlled rotational speed mechanisms for each motor, and an inclination or azimuth controller to decrease or increase the speed of either a bottom motor, a top motor, a right motor or a left motor; and a method of drilling using the directional drilling system
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Conventional boring techniques traditionally operate with a boring device or machine that pushes and/or rotates a drill string consisting of a series of connected drill pipes with a directable drill bit to achieve an underground path or direction through which a conduit or utility device can be installed. Traditional methods of drilling include a drill body and a drill blade that is usually concentric in design and creates a cylindrical hole about the same diameter as the drill blade. Traditional methods and devices typically use high pressure high velocity jetting to steer and cool the drill body and blade.
Wells are drilled directionally for several purposes. These purposes include increasing the exposed section length through the reservoir by drilling through the reservoir, drilling into the reservoir where vertical access is difficult or not possible, allowing more wellheads to be grouped together on one surface location, and drilling along the underside of a reservoir-constraining fault to obtain multiple productive positions.
Most directional drillers are given a preplanned well path to follow that is determined by engineers and geologists before the drilling commences. When the directional driller starts the drilling process, periodic surveys are taken with a downhole instrument to provide survey data (inclination and azimuth) of the well bore. These measurements are typically taken at intervals between 30-500 feet, with 100 feet common during active changes of angle or direction. Modern directional drilling (DD) systems include a downhole MWD (measurement while drilling) tool to provide continuously updated measurements used for real-time adjustments.
These MWD data indicate if the well is following the planned path and whether the orientation of the drilling assembly is causing the well to deviate as planned. Corrections are regularly made by adjusting rotation speed or the drill string weight (weight on bit).
One of the basic problems of a directional driller is to accurately set a specific tool face orientation. After a connection, the driller must rotate the pipe at the surface and experiment with the weight-on-bit and top drive quill position to orient the tool face. The driller has to work with throttles, clutches, brakes, and a forward or reverse control to orient the drill pipe to the correct position. The challenge is to properly orientate the down hole tool to steer the well bore in a desired direction.
The most common method of drilling oil wells consists of rotating a cutting bit comprising individual cone bits which is attached at the bottom of a hollow drill string of pipe and drill collars to progressively chip away the layers of earth. To force the chips of rock and earth formation to the surface, the common practice has been to force a fluid known as “drilling mud” or “drilling fluid” down the hollow drill string, thence outwardly between the cutting teeth to clear the teeth of accumulated dirt, and thence out into the annulus formed between the wall of the well which is being drilled and the exterior of the drill string. The mud picks up the chips of rock and earth and carries them with it to the surface to clear the well as it is drilled progressively deeper.
A typical cutter layout comprises three conical cutters of a rolling cone drill bit. The cutters are located in a non-planar relationship and are typically tilted inward or outward. Each cutter comprises a generally conical body upon which are circumferentially located raised insert lands arranged circumferentially around the conical surface of the cutter. Hard metal cutting elements, commonly termed “inserts”, are located in cylindrical bores drilled into the cones perpendicular to the surface of lands.
Drilling mud has a number of desired properties. It has a high viscosity and high density which makes it capable of carrying the cuttings from the rotating cutting bit up the annulus to the surface at a relatively low velocity of about 125 to 150 feet per minute. Should mud circulation be temporarily stopped, the settling velocity of cutting is reduced. By reason of its high density, the mud tends to buoy up the drill string thereby to reduce the strain on the drilling rig, and mud in the annulus is at a high hydrostatic pressure which is exerted outwardly against the wall of the well and helps to prevent cave-ins and blow-outs which might occur as the result of high formation pressure. Additionally, finely divided solids suspended in the drilling mud work to build a filter cake on the wall of the well, frequently termed a bore hole, thus reducing loss of mud which might otherwise filter to the formation. The mud also serves to lubricate the bore hole wall. A further attribute of mud is that of lubricating the bearings of the cone bits, and keeping them relatively cool. The mud further serves as a medium through which various types of logs are communicated to determine characteristics of the formations which have been penetrated as drilling progresses.
In oil well drilling, directional bores (other than straight) are often drilled to recover oil from inaccessible locations; to stop blowouts; to sidetrack wells; to by-pass broken drill pipe; and for various other reasons.
Conventional techniques for directional drilling in wells use a deflector in the borehole to push the bit sideways (e.g. “whipstocking”); or alternatively insert a bent joint in the drilling string (e.g. “bent subs”); or alternatively propel pressurized drill mud sideways through a nozzle in the drill to push the bit sideways (e.g. “side jetting”).
The “whipstocking” process requires a series of separate operations including drilling of a pilot hole, reaming of the pilot hole to full gauge, and removal of the deflector, and is therefore a time consuming and costly process. The use of “bent subs” to produce lateral forces on the drill bit requires the use of expensive drill motors; and the “side jetting” process, using special drill bits to provide offset holes by the pressurized drill mud, does not function well in hard rock earth since the conventional mud pressures will not erode the hard rock materials.
Various forms of earth boring bits are utilized to cut through the hard material formations in the earth when forming a well bore. One general form of the drill bit utilizes one or more rolling cutters whose outer surfaces include projections such as milled teeth or cutter inserts that gouge into the formation material causing the material to disintegrate or pulverize as the cutter is rotated when the tool is turned about its axis. The rolling cutters are individually mounted to rotate about a supporting shaft or spindle typically with the axis of the spindle spaced radially from and at an incline with respect to the rotational axis of the tool. The incline of the spindle axis causes the cutter to both rotate about its axis and roll relative to the bottom of a borehole as the bit body is rotated. As a result, the cutter disintegrates a concentric ring of formation material in the bottom of the borehole.
One earlier version of the foregoing general type of rolling cutter is disclosed in U.S. Pat. No. 3,389,760. The patent discloses a rolling cone cutter supported to rotate upon a load pin which is connected at its opposite ends to a generally U-shaped support saddle. As disclosed, a number of such saddle and rolling cutter arrangements may be mounted on a single bit body for drilling a large borehole. For disintegrating formation, a multiplicity of small inserts of cemented tungsten carbide are fitted into drilled holes in each cutter body. The inserts are disposed in overlapping rows so that as the cutter is rolled over the bottom of a hole the inserts cut overlapping tracks so as to disintegrate the formation over the full width of a concentric swath defined by the length of the cutter as it is rotated around the axis of the drill bit. The cutting elements of U.S. Pat. No. 3,389,760 are in somewhat of a semi-random pattern on a smooth outer surface of the cutter. This physical arrangement of cutting elements leaves certain lateral discontinuities in the bottom hole pattern. As a result, the non-uniform succession of cutting elements often imparts an abrupt impact force during rotation of the cutter. Moreover, by design the outer surface of the cutter does not have relief grooves which initially aid in carrying away a disintegrated formation with the drilling fluid.
Ruhle (1972), U.S. Pat. No. 3,692,125, discloses a combination drilling and stimulation process for drilling oil wells. A drilling head in which the drilling mud flows outside the drilling string, which the mud carrying rock chips flows inside the inner pipe is described. The drill cones are arranged for better clearing of the rock chips. However the use of a clear solution containing calcium chloride instead of the usual drilling mud is disclosed. The solution of calcium chloride is treated with a liquified surfactant, and the mixture is forced down the annulus formed between the drill pipe and drill collars, and the wall of the drill hole. At the bottom of the well the solution passes the cutting face of the bit and picks up the chips, flushing them outwardly through the drill collars and drill pipe and out at the top. The arrangement is aimed at the traditional vertical drilling only, and did not include any means for directional drilling.
Jones (1983), U.S. Pat. No. 4,420,050, discloses an oil well drilling bit of the type utilizing hard metal inserts in the rolling cutters wherein each row of inserts on each cutter is located thereon in a sinusoidal or varying pattern rather than the strictly circumferential pattern of the prior art.
Dardick (1986) U.S. Pat. No. 4,582,147, proposes a system for directional drilling of boreholes into the earth under control of the driller at the surface, employing a rotating earth drill including a projectile firing mechanism, that is timed to non-symmetrically repetitively fire repeatedly projectiles into the earth at controlled angular positions that are offset from the axis of the drill and drill string in the desired direction of drilling, as the drill progresses into the earth, thereby to fracture and break the rock in a desired direction other than straight ahead of the drill. The advancement of the rotary drill into the bore therefore follows a controlled path in the direction desired.
To remotely control the drill to fire the projectiles at a desired offset position or location as the bit rotates, the angle of rotation of the drill string is monitored at the surface, and the firing of the projectiles is remotely controlled from the surface to be “timed” to occur when the firing mechanism is rotatively positioned at a desired angle.
Wu (1993) U.S. Pat. No. 5,230,386, (reissued Re 35,386 December 1996), discloses a method for detecting and sensing boundaries between strata in a formation during directional drilling so that the drilling operation can be adjusted to maintain the drill string within a selected stratum. The method comprises the initial drilling of an offset well from which resistivity of the formation with depth is determined. This resistivity information is then modeled to provide a modeled log indicative of the response of a resistivity tool within a selected stratum in a substantially horizontal direction. A directional (e.g., horizontal) well is thereafter drilled wherein resistivity is logged in real time and compared to that of the modeled horizontal resistivity to determine the location of the drill string and thereby the borehole in the substantially horizontal stratum. From this, the direction of drilling can be corrected or adjusted so that the borehole is maintained within the desired stratum.
Thompson (1995) U.S. Pat. No. 5,425,429, proposes a method for forming lateral boreholes from within an existing elongated shaft. A drilling unit is positioned within the existing shaft, bracing the drilling unit against a wall surrounding the existing shaft to transmit forces between the drilling unit and the medium surrounding the wall, and applying a drilling force from the drilling unit to cut through the wall of the existing shaft and form the substantially lateral borehole in the surrounding medium. The method includes an extendable insert ram within the drilling unit for extending a drill bit from the drilling unit and applying a drilling force to the drill bit to cut through the wall of the existing shaft. A supply of modular drill string elements are cyclically inserted between the insert ram and the drill bit so that repeated extensions of the insert ram further extends the drill bit into the surrounding medium to increase the length of the lateral borehole. The method has no provision for true directional steering and is not suitable for oil drilling, as the extensions of the lateral drilling string is limited by collars that can only fit within the main hole.
Saxman (1995) U.S. Pat. No. 5,429,201, discloses an improved bit design in which the drill bit includes a rolling cutter having a plurality of circumferential rows of teeth protruding from the body of the cutter. At least one of the rows of teeth is a closed-end circumferential row located on the surface of the cutter along a closed-end circumferential path. The latter is a non-circular curve defined by a surface intersecting the body of the cutter obliquely with respect to its longitudinal axis.
Gipson (1995) U.S. Pat. No. 5,439,066, discloses a method and system for translating the orientation of a length of coil tubing from a generally vertical orientation to a generally horizontal orientation, inside a well borehole and downhole of a wellhead. A first conduit is installed and suspended in a well borehole. The conduit is provided with a coil tubing bender at the downhole end of the conduit. Coil tubing is injected into the conduit through an upper packer attached to the top section of the conduit. After a section of coil tubing is injected into the conduit, an outer coil tubing seal is securely affixed to the coil tubing. The coil tubing is run to the top of the bender; the packer is closed; and high pressure fluid is introduced between the upper packer and the outer seal inside the conduit. The fluid forces the coil tubing through the bender and translates the coil tubing from a vertical to horizontal orientation. Abrasive fluid may be pumped at high pressures through the coil tubing now in the horizontal orientation, thereby creating a horizontal bore in the formation.
Hathaway (1996) U.S. Pat. No. 5,553,680, discloses a horizontal boring apparatus which is comprised of a remotely controlled drilling tool lowered from a self-contained vehicle into a previously drilled vertical shaft. The tool mills away a 360 degree band of metal casing adjacent to the desired area to be bored, and extends a hydraulic powered rotary drilling tool into the formation by extending and retracting a telescoping base while alternating stabilization of the base and bit end of the drilling tool. The tool is designed to drill a 1 inch bore hole up to 150 feet in any direction, or several directions. The tool and tool housing contain instrumentation for sensing direction, inclination, density, and temperature.
Kuenzi (2001) U.S. Pat. No. 6,308,789, discloses a drill bit that is arranged to change the direction of drilling. A cone head is rotatably mounted on a shank portion extending from an elongate housing. When the housing is rotated, the cone head generates a concave hole. When a change in direction is required, the housing is rotated a few degrees in one direction and then counter-rotated in the opposite direction. This generates a partial but redirected pilot hole that is also substantially concave in configuration. Continued full rotation causes the drill bit to follow the partial pilot hole in the new direction.
Smith (2002) U.S. Pat. No. 6,386,298, discloses a hole opener and method for using same which allows for a greater number of cone utters to be attached to the hole opener. The support structure provided by the present invention uses a barrel which is attached to the drill stem to effectively increase the diameter of the drill stem so that additional cutters may be attached to the hole opener. Using the barrel structure, the structural integrity of the tool is not compromised, and a strong support structure for the cutters is provided. The cone cutters may be removable from the barrel. The removable structure is provided by placing a bolt inside the segments which is used to mate the segment with a pocket attached to the barrel. This results in a very versatile tool in that the same boring head may be used for boring various types of materials. The barrel structure of the present invention also provides a means for trapping cones inside the barrel to prevent the cone cutters from being left inside the hole. The tapered shape of the hole opener allows it to be forced back to the point of entry after drilling in order to displace debris.
Haci et al. (2004) U.S. Pat. No. 6,802,378, discloses a method of and system for directional drilling reduces the friction between the drill string and the well bore. A downhole drilling motor is connected to the surface by a drill string. The drilling motor is oriented at a selected tool face angle. The drill string is rotated at said surface location in a first direction until a first torque magnitude without changing the tool face angle. The drill string is then rotated in the opposite direction until a second torque magnitude is reached, again without changing the tool face angle. The drill string is rocked back and forth between the first and second torque magnitudes.
Mcloughlin el al. (2004) U.S. Pat. No. 6,808,027, proposes an apparatus for selectively controlling the direction of a well bore comprising a mandrel rotatable about a rotation axis; a direction controller means comprising at least two parts configured to apply a force to said mandrel with a component perpendicular to the said rotation axis; a housing having an eccentric longitudinal bore forming a weighted side and being configured to freely rotate under gravity; and a driver for selectively varying the angle of the force relative to the weighted side of the housing about said rotation axis, the driver being configured to move the two parts independently of one another.
Sved (2004) U.S. Pat. No. 6,810,971, discloses various steerable horizontal subterranean drill bit apparatuses, which may have a drill bit, a housing and a one-bolt attachment system, or other features.
Adam et al (2007) U.S. Pat. No. 7,195,082, discloses a method of steering a fluid drilling head in an underground borehole drilling situation is provided by rotating the flexible hose through which high pressure is provided to the drilling head and providing a biasing force on the drilling head. The hose can be rotated from a remote surface mounted situation by rotating the entire surface rig (13) in a horizontal plane about a turntable (24) causing the vertically orientated portion of the hose (11) to rotate about its longitudinal axis. The biasing force can be provided in a number of different ways but typically results from the use of an asymmetrical gauging ring on the fluid drilling head.
Russell (2009) U.S. Pat. No. 7,543,658, discloses a drilling means for directional drilling in a bore hole comprising a drill pipe and a drilling head, including a slippable clutch device linking the drill pipe and said drilling head such that torque due to rotation of said drill pipe can be controllably applied to said drilling head through at least partial engagement of said clutch, and control means operable to sense an actual orientation angle of said drilling head and compare said actual orientation angle with a required orientation angle adjustably set in said control means and to control said slippable clutch such that when the actual orientation angle and the required orientation angle are the same, the slip torque of the slipping clutch equals the motor reaction torque, so maintaining the orientation angle of the drilling tool at said required orientation angle.
Al Hadhrami (2011) U.S. Pat. No. 7,958,949, discloses a technique for drilling a borehole includes obtaining data from a tool in the borehole for a plurality of positions in the borehole that is being drilled to form acquired data indicative of directional electromagnetic propagation measurements. The technique includes identifying a plurality of distances to a boundary between formations in ground from the plurality of positions in the borehole based on the measurements; identifying a trajectory of the borehole using the plurality of distances; and deciding whether to change the trajectory of the borehole using a change in the plurality of distances between the trajectory and the boundary. The trajectory of the borehole may be changed in both inclination and azimuth.
The disclosure described herein is to provide improved apparatus and control methods for directional drilling. The invention discloses mechanisms for effective steering of the drilling head by introducing four independent motor-driven drilling bits in addition to other unique features to simplify the drilling operation.
In summary, the traditional design of the drill bit attempts to utilized the rotational power of the drilling system for crushing rock while removal of debris is performed using the drilling fluid. On the other hand, the design of the drilling bits disclosed herein is such that the drill bit performs rock crushing and contributes as well to debris removal. In fact, the difference between the debris removal rates of each of the four drilling bits permits directional drilling.
The present disclosure discloses a drilling apparatus with four drilling motors. The apparatus disclosed herein eliminates the need for the current complicated techniques, and provides simple and intuitive techniques for precise drilling of the desired hole bore trajectory.